My 94 cherokee with a 5 speed, external slave, is messing up.
When i hold the clutch down it looses pressure and i have to pump a few times. Normal shifting, up and down when shifting it works and feels fine..
Also poped the cap to see if the fluid was low and its maxed to the top. Nevwr have has an issue in 20k+ since i bought it.

 

i would try to bleed it first but either the master cylinder or slave cylinder is probably bad. Your lucky your slave is external.

 

Im assuming ones bad...tried to bleed it tonight but from my knowledge its a sealed system?..
And yes, my 90 xj was internal slave...had to replace it twice! what a job.

 

Replace it.